The present invention relates to a filtering apparatus, comprising at least one filter element placed into a filter housing supported by a casing, the filter element being provided with an inlet assembly for the liquid flow to be filtered, an outlet assembly for the filtered liquid flow, an air channel for cleaning the filter element by flushing with air during the filtering stages, and a separate filling assembly for filling the housing with liquid before initiating the next filtering stage after flushing.
Continuous automatic filters, in which filtering and flushing stages alternate, are used, for example in diesel motors for filtering fuel or lubricant. Filtering is used to remove the principally solid impurities wearing the motor.
Filtering apparatuses applicable for the above-mentioned purpose are known, in which the filtering is conducted alternately in two or several parallel filtering chambers, controlled by a rotating spindle acting as a valve. The cleaning of the filtering chambers is performed by backflushing between the filtering stages. An apparatus of this type is disclosed in U.S. Pat. No. 4,256,583.
As filtering again occurs after the flushing stage in the filter housing, it is advantageous to fill the filter housing slowly and controllably with liquid before initiating the filtering. The intention is to get air removed from the filter housing as completely as possible, as its mixing with the filtered fuel or lubricating oil would be detrimental.
An automatic filter is known, in which the filter housing is prefilled with clean filtered liquid directed into the housing from an opening arranged in the spindle controlling the parallel filter housings. The upper end of the filter housing in the filter is provided with a float, which closes the exit route for air, as the housing is filled with liquid. Filtering is then initiated in the filter housing from the inlet assembly in the spindle through the jacket of the filter element as a flow-through into the outlet assembly in the spindle.
A drawback in the above filter is that the filling assembly in the spindle is always open in the direction of the filter housing, which prevents the opening of the housing for changing the filter elements or for other servicing measures. Opening the filter housing would result in the discharge of the liquid under pressure out of the housing. It would be difficult to close the filling assembly in this filter, and it would require that the structure of the spindle be changed.
The object of the present invention is to provide a solution for the perceived drawbacks in the art, so that the filling assembly for prefilling the filter housing with liquid does not prevent the opening of the filter housing for servicing measures. It is characteristic of the filtering apparatus of the invention that the filling assembly is formed by a filling channel led through the casing of the filter housing, the channel being provided with a valve for closing the channel upon opening the filter housing.
The filling channel arranged according to the invention for prefilling the filter housing is advantageous especially in the filtering apparatus in accordance with the applicant""s previous patent application FI 982113, filed Sep. 30, 1998, which has three filtering units controlled with a common valve. Two of the units are meant to operate alternately in the actual filtering process, at the same time as the third unit forms a reserve unit, into which the flow to be filtered is directed during the service of the first two units. The performance of such an apparatus requires that either of the first two units may be opened, for example, for changing the filter elements, without separate measures as soon as the filtering flow has been transferred to the reserve unit.
According to an advantageous embodiment of the invention, the filter housing is supported by a stationary casing, and is provided with a removable cover, and the valve is provided with a spring, which is arranged to achieve the closing of the valve as the cover is opened. In other words, as the cover of the filter housing is opened, the valve will automatically close the filling channel.
The cooperation of the cover and valve may be achieved, for example, with a bar affecting the compression spring in the valve, the bar moving from its place pushed by the spring as the cover is opened so that the spring simultaneously closes the valve. At the same time, the bar may advantageously be arranged as a support for the filter element or elements in the filter housing.
It has to be possible for the air remaining in the housing after the flushing stage to leave the housing during the prefilling of the filter housing through the filling channel, for which purpose the housing may be provided with an air vent at its upper end. Closing the channel after the filter housing has been filled with liquid may be achieved, for example, with the help of a float raised by the liquid. An axle formed from a tube may advantageously be used as the air vent, the axle working simultaneously as a support for the filter elements arranged around it.
Alternatively, air may be arranged to be discharged from the filter housing into a separate air container, into which air is compressed, pushed by the liquid filling the housing. The air container may be separated from the center of the filter housing and formed as part of an axial element, which from its lower end affects the compression spring of the valve in the filling channel so that the element makes the valve close as it moves from its place.